Email has become an important method for communicating. Email systems typically include a server component (e.g., Microsoft Exchange Server) and a client component (e.g., Microsoft Outlook or Microsoft Outlook Express). These components are typically software applications that are configured to execute on computing devices (e.g., servers, PCs, laptops, and PDAs).
Often, in order to facilitate communications, a client and server, such as client component and a server component of an email system, agree on a communications protocol. The protocol sets out the rules defining the expected behavior of each party during communications, for example, the expected sequence of request and response. Sophisticated protocols have rules for handling unexpected behavior.
As client and server components are improved, the improved versions are distributed to end users. In order to take advantage of new component features and network features, it is often the case that a new communications protocol is invented. Where the installed base of server components is significant, a client component may have the ability to communicate, via a set of protocols, with selected previous versions of server components.
It is sometimes the case that later protocols build upon earlier protocols rather than replacing them wholesale. In such a case, a later protocol may be built of protocol elements which can be enabled or disabled in order to simulate earlier protocols. Likewise, where the installed base of client components is significant, a server component may have the ability to communicate, via a protocol, with selected previous versions of client components.
The invention provides such a system and method. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.